Machine Screws Key Terms

Understand terminology related to machine screws to make smarter business choices

By Howard Robertson

Machine screws are essential components of industrial equipment. Apart from fastening, these screws also serve as a member of a drive system for an industrial machine. Mostly, fastener manufacturers use metals and alloys for manufacturing these screws.

If you want to buy machine screws, you will need to be conversant with certain terms that indicate specifications, types or measurement units for these screws. This guide will introduce you to some technical terms, such as lead angle, major diameter, pitch and ball screws.

Lead angle

Lead angle is the angle made by the helix of a screw thread with a plane perpendicular to the screw axis.
Try: To understand the definition of lead angle, read through the glossary of technical terms at All American Security Fasteners, a supplier of industrial fasteners.

Major diameter

Major diameter is another important specification of a machine screw. It can be defined as the diameter of an imaginary cylinder parallel with the crests of the threads of a machine screw.
Try: Bolt Depot, an online retailer of fastener products, provides definitions for various fastener terms, including major diameter.

Minor diameter

This is another diametric specification of machine screws. It is defined as the diameter of an imaginary cylinder that just touches the roots of the threads of a machine screw.
Try: Allmetal Screw Products, a manufacturer of stainless steel fastener products, offers a glossary of important fastener terms. You can also read through the thread glossary at eMachineShop.

Pitch

Thread pitch (or pitch) is the distance from a point on a screw thread to the corresponding point on the next thread, measured parallel to the axis of the machine screw.
Try: For definition of thread pitch, read through the glossary of technical terms at Roton Products, a supplier of industrial screws. Bolt Science also offers a glossary of technical terms related to nuts, bolts and screws.

Metric dimensions

Metric dimensions are the dimensions of industrial products according to the Systeme Internationale (SI) standards. For machine screws, the length and diameter is measured in millimeters or centimeters, according to the SI standards.
Try: For basic information on metric dimensions, read through the masonry glossary at Woodruff Block Company.

Imperial dimensions

Unlike metric dimensions, the imperial measurement system specifies lengths of machine screws in inches.
Try: Technology Services (PDF), a part of the National Institute of Standards and Technology, provides an informative document that explains the relation between different measurement units. You can also read through the definitions for the imperial units by the University of North Carolina at Chapel Hill.

Cold or hot forming

As the name indicates, a cold forming (or cold working) process is a metal forming operation carried out at room temperature. A hot forming process is carried out at high temperatures, as the yield strength of a metal or alloy is less at higher temperatures.
Try: To understand the concept of cold forming, read through the fasteners glossary at Marsh Fasteners, a reputable supplier of industrial fasteners. Sandmeyer Steel Company, a supplier of industrial steel products, offers a glossary of technical terms, including cold forming and hot forming.

Ball screws

A ball screw is a special type of machine screw that can be used to convert rotary motion to linear motion or torque to thrust. These screws are useful for industrial drive systems as they have very low friction.
Try: Sherline Products, a supplier of machine tools, offers a glossary of technical terms, including ball screws.